Composite strut



Dem, 111, 1923. 1 477 3611 R. KEMP COMPOSITE STRUT Filed July 22 1 1-918 l I I 'INVENTOR WITNESSES: I 50! flab erfi fiemp 1 BY I a TORNEY Patented Dec. ll, 11923.,

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. COMPOSK'EE STRUT.

Application filed duly 22, 1918. Serial No. 246,017.

To all whom it may concern:

Be it known that 1, ROBERT Kenna citizen of the United Sates, and a resident of Washington, District of Columbia, have ina vented a new and useful Improvement in Composite Struts, of which the following is a specification.

My invention relates to improvements in reinforced tubular elements and, more particularly, to reinforced tubular elements used in the construction of aircraft, and it' has for its primary object the construction of a composite tube comprising an inner reinforcing portion of material of great com- 1 pressive strength and an outer sleeve having great tensile strength.

Tubular elements of metal, as, for instance, steel tubes, have relatively great tensile strength but comparatively small compressive strength and are, therefore, subject to buckling. For this reason, one object of my invention is to provide a reinforcing material for metallic tubes that will greatly resist any tendency of such tubes to buckle.

In aircraft construction, it is advantaeous to have structural elements that are ight in weight and strong and that have relatively small surface areas exposed to air currents. In view of this, another object of my invention is to construct tubular elements that possess the above mentioned advantages and may be used for structural elements in aircraft.

Another object of my invention is to construct a composite tube which will oller a comparatively high resistance to bullet penetration. I a

A still further object of my invention is to construct a tubular element which will be substantially free from liability to internal corrosion and which will be non-inflammable.

With these and other objects in view, a better understanding of my invention may be had by reference to the drawings, in the several fi ures of which corresponding numorals re er to like parts. Fig. 1 is a longitudinal, diametral section of a tubular element in the course of construction, show- 50 ing a two-part mandrel, partly in elevation and partly in section, in its initial position; Fig. 2 is a longitudinal, diametral section of a tubular element showing a twoart mandrel in elevation after pressure has con applied to it and the two parts of the mandrel have been forced into their final positions; Fig. 3 is a plan view, parts being broken away, of a sheet used as reinforcing material in constructing a tube in accordance with my invention.

n1 practising my invention, 1 may wind a sheetof suitable material around a sectional mandrel and place the mandrel, with the sheet wound on it, within a tube. The mandrel is adapted to exert an expansive force against the material disposed about it by reason of having its sections s aced in their initial positions to allow after the mandrel and the material disposed or their movement, under the application of pressure,

about it have been placed in the tube or sleeve. The reinforcing material may then be hardened in any suitable manner, as by the application of heat. The material, thus forced into contact with the enclosing sleeve and hardened while in that relation adheres vepRy tenaciously to the sleeve.

eferring to the drawings, 1 is a two-part mandrel, the sections of which are initially spaced as shown at 2 and slidably connected by means of the dowel or pin 3 seating in a recess a, the mandrel sections being tapered from their outer to their inner ends, which are adapted to be forced together. under pressure, to exert an expansive pressure on material wound about them. The inner reinforcement 5 is made from the tapered sheet 6, shown in Fig. 3, which is wound on the two-part mandrel 1 by starting with the tapered end of sheet 6 and continuing the winding operation until the complete sheet is disposed in layers about the mandrel.

The sheet 6, thus wound on the mandrel i may be a sheet of closely matted, calendered material, such as paper, a loosely matted or spinnable fibrous material, such as cotton batting, or a woven material, such as duck or muslin, and the sheet may be treated with a binder, such as shellac, copal,

into close contact with the sleeve 7. Heat may be applied to the body thus built up, either while the separate parts of the mandrel are being forced together or after the mandrel sections are in their final positions, as shown in Fig. 2. The applied heat hardens the material 5 and firmly cements it to the sleeve 7.

The proportions of the several parts used in the construction of the tubular element, as shown in the drawings, are greatly exaggerated to accentuate the different steps employed in its construction.

These and other like methods may be used in constructing tubular elements in accordance with my invention by any one skilled in the art andit is, therefore, to be understood that no limitations are to be imposed upon my invention other than those indicated in the appended claims.

I claim as my invention:

1. A tubular element comprising a sleeve and a reinforcin body disposed therein which varies in thickness of wall from its intermediate portion to its ends.

2. A tubular element comprising a sleeve and a laminated reinforcing body which tapers from its central portion to its ends enclosed therein.

3. A tubular element comprising a sleeve enclosing a body of laminated reinforcing material treated with a binder which has been hardened by the application of heat and pressure.

4. A tubular element comprising a sleeve and an enclosed reinforcing body of superimposed laminations of sheet material impregnated with a binder which has been hardened by the application of heat and pressure. I

5. A tubular element comprising a metallic sleeve and an enclosed reinforcing" body which varies in thickness of wall from its central portion to its ends.

6. A tubular element comprising a metallic sleeve and an enclosed reinforcing body of superimposed laminations of sheet material impregnated with a phenolic condensation product which has been hardened by the application of heat and pressure.

7. A tubular element comprising a metallic sleeve and an enclosed reinforcing body of superimposed laminations of sheet material constituting an inner wall which varies in thickness from its intermediateportion to its ends, the reinforcing material being impregnated with a phenolic condensation product which has been hardened by the application of heat and pressure.

8. A tubular element comprising a sleeve and a reinforcing body of superimposed laminations of fibrous material which has been treated with a binder molded therein.

9. A tubular element comprising a metallic sleeve and a reinforcing body of fibrous material impregnated with a binder molded within the sleeve and having its wall tapering in thickness from its intermediate portion to its ends.

In testimony whereof, I have hereunto subscribed my name this 18th day of July, 1918.

ROBERT KEMP. 

